Bending and metallurgical properties of rotary endodontic instruments. IV. Gates Glidden and Peeso drills.

A laboratory study was performed on Gates Glidden and Peeso drills to determine the bending characteristics and related metallurgical properties. Sizes #1 to #6 stainless steel Gates Glidden drills, sizes #1 to #6 stainless steel and carbon steel type P Peeso drills, and sizes #009 to #023 carbon steel-type B-1 Peeso drills were evaluated in cantilever bending with a Tinius Olsen stiffness tester. The bending moments were measured for a 12.5-mm test span at deflection angles of 2 to 90 degrees. The mean maximum bending moments in g cm and the corresponding deflection angles in degrees were plotted graphically to ascertain the bending characteristics of the instruments. The stainless steel Gates Glidden and Peeso drills exhibited considerable permanent bending deformation during testing. Some stainless steel drill samples were able to withstand the full bending deflection of 90 degrees without fracturing. In contrast, the carbon steel Peeso drills were able only to undergo bending deflections of less than 20 degrees and exhibited brittle fracture. If the drill fractured during the in vitro testing, the failure site was always located near the handpiece end.